Lass with a soldier on two sides (4)
I believe the answer is:
girl
'lass' is the definition.
(lass can mean a young woman)
'soldier on two sides' is the wordplay.
'two sides' can mean two replacements for 'side'.
'soldier' becomes 'GI' (GI can mean a US soldier).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'side' becomes 'r' (abbreviation for right).
'side' becomes 'l' (abbreviation for left).
'gi'+'r'+'l'='GIRL'
'with a' acts as a link.
(Other definitions for girl that I've seen before include "Maidservant" , "Miss" , "Maid" , "See 5" , "One of 8 [LASSES]" .)